The present invention relates generally to a railway hopper car for transporting loads of bulk materials. More specifically, the invention relates to a hopper car gate having reduced opening torque.Railway hopper cars are widely used to transport loads of bulk agricultural commodities, such as soya meal, and chemical commodities, such as hydrated alumina, potash, and soda ash. The bulk materials are loaded through the top of the car and unloaded through a gate at the bottom of the car. This gate typically is opened manually by a rack and pinion assembly or other mechanical system to allow the load to drop out beneath the hopper car. Certain loads can be particularly difficult to unload. For example, alumina is heavy and has a tendency to compact during transportation. Soya meal also may tend not to flow after the gate has been opened.
One approach to facilitating unloading of hopper cars has been to provide oversized gates that are about 25% larger than those generally used in the past. The increased size of the gate increases the force experienced on the gate, however, such that opening torque may be unacceptably great. Additionally, new regulations require improved seals on the gate in order to minimize leakage of the load around the sides of the gate, which further contributes to high opening torque.
In the past, efforts to reduce opening torque of railway car hopper gates have attempted to address problems associated with the functioning of the mechanical system used to open the hopper car gate. For example, U.S. Pat. No. 4,475,672 issued to Whitehead addresses the problem of caking and freezing of water mixed with dirt, grain and other materials in the rack and pinion assembly, which can result in jamming of the door. A hopper discharge device is disclosed that is designed both to prevent accumulation of material in the working mechanism and to self-clean. To this end, a gate is provided having one or more inverted channel members on the underside of the gate with each member including a section of roller chain. The edges of the gate rest on either side in a gate guide which is part of a gate support. Wear strips manufactured from anti-friction materials provided on either side of the undersurface of the gate engage the surface of the gate guide on which the gate rests on both sides to help reduce friction as the gate slides open and closed along the gate guide.
In addition to clogging of the gate mechanism, corrosion of the metal parts of the mechanism can increase opening torque. Some gates have employed bushings or other components made of a low friction material such as Teflon in place of rollers to avoid problems associated with corrosion. The hopper car gate mechanism disclosed in U.S. Pat. No. 5,046,432 issued to Bowler addresses the problem of corrosion of the components. This patent states that by providing for a slider means comprised of one or more elongated bodies made of some low-friction composite material, the gate slide will not corrode and is permitted to open and close freely without sticking or jamming.
There remains a need for an improved hopper car gate which can offer consistent and reliable gate operation and discharge of lading without excessive breakaway opening torque even after extended use and exposure to harsh weather and other adverse environmental conditions over its useful life.